Increasing power and I/O demands in HDI (high density interconnect) components coupled with the industry-wide conversion to lead-free products has introduced additional risk for solder joint reliability (SJR) of BGA (ball grid array) Flip-Chip electronic packages. One particular concern is SJR under mechanical shock (dynamic bend) loading. While leaded alloys provided good performance in shock for many years due to the unparalleled ability of lead's slip systems to absorb the energy in shock events, lead-free alloys cannot provide the same benefit. To mitigate this risk, better approaches for understanding damage propagation are needed to enable better design to limit and reduce the SJR risk during shipping and end-user handling.To this end, a characterization study is undertaken to monitor damage progression at the second-level interconnect in BGA's on flip-chip electronic packages during mechanical shock loading. The study uses a board-level, strain-monitoring approach plus the dye and peel failure analysis technique to track the initiation and propagation of solder joint cracks under loading. The approach being used differs from conventional reliability testing in that both design and load variables are used to quantify damage growth and strain response to bridge the understanding of design feature impact to traditional reliability testing. The scope of the study includes investigating the impact of such factors as package placement, board layout, and enabling load on the monitored board strain and the damage propagation observed. From this study, directions and design guidelines for improving solder joint reliability of future BGA's on flip-chip electronic packages under mechanical shock loading conditions are proposed.
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